Skip to main content
To KTH's start page To KTH's start page

Cycle paths’ degradation processes and surface condition assessment

Time: Tue 2023-03-21 13.00

Location: B3, Brinellvägen 23, Stockholm

Video link:

Language: English

Subject area: Civil and Architectural Engineering, Building Materials

Doctoral student: Martin Larsson , Byggnadsmaterial, VTI - Statens väg- och transportforskningsinstitut

Opponent: Professor Inge Hoff, Norwegian University of Science and Technology

Supervisor: Adjungerad professor Sigurdur Erlingsson, Byggnadsmaterial, VTI - Statens väg- och transportforskningsinstitut; Doktor Anna Niska, VTI - Statens väg- och transportforskningsinstitut

Export to calendar

QC 20230227


A shift in modal share from car driving to cycling has many benefits, both from individual- and societal perspectives, e.g., better health from an increase in physical activity, lower levels of pollution and congestion. However, there are also some potential problems with such a shift. Cyclists have a higher risk of traffic incidents per travelled kilometre than car drivers. This risk needs to be minimized for an optimal transition to more cycling. A smooth surface with good friction on the cycle path is not only important for the traffic safety of the cyclists but also for their comfort and level of service. Potholes, cracks, and bumps are frequent obstructions on the cycle paths. These are all maintenance-related deficiencies associated with the degradation of the structure. In general, the knowledge on degradation of roads is good, as there is a long tradition of investigation into the degradation factors. Cycle paths, even though constructed with similar materials and techniques as the roads, are however not designed in the same way as roads, mainly since they will not be subjected to the same traffic load. Thus, one purpose of this licentiate thesis is to identify degradation factors specific for cycle paths, through a state-of-the-art literature study. This literature review is complemented by two papers, where Paper A analyses the distress found on Swedish municipal cycle paths and Paper B evaluates a novel method for condition assessments on cycle paths related to cycling comfort—the Bicycle Measurement Trailer. The review and papers are meant to act as the basis for the general aim of the PhD-project, namely, to develop more knowledge on the degradation of cycle paths. This knowledge is needed to improve the structural design approaches and maintenance strategies for cycle paths and to give guidance for preventive measures to inhibit degradation. A literature search in the national and international transport research databases was conducted, along with consultations in guidelines and handbooks on cycle infrastructure, in particular the official guidelines ofTrafikverket (the Swedish Transport Administration). Paper A is based on a state-of-practice survey in the Swedish municipalities where the stated distress modes and causes were analysed with respect to climatic and population data. The most common distress modes on municipal cycle paths in Sweden from previous studies—cracks, surface unevenness and edge deformation—were confirmed. The municipalities with main urban areas with a population of 60,000–120,000 habitants stand out from the general trend in that they seem to have less distress on their cycle paths. Further investigations are needed to find the main reasons behind this. For Paper B, field tests were conducted to establish the accuracy and repeatability of the proposed condition assessment tool, and the collected data was used to assess five different metrics for longitudinal evenness of cycle paths. The Bicycle Measurement Trailer was found to be a promising technique for condition assessment on cycle paths as it shows a high accuracy when compared to the standardized road measuring system, Road Surface Tester. The repeatability is also high. More studies are however needed to evaluate its ability to detect different distress modes. Such studies should proceed from the Evenness Coefficient metric. The conclusions of the thesis suggest that the structural design principles for cycle paths in present guidelines are insufficient for the optimization of the construction of cycle paths. They appear to be an adaptation of the structural design principles of low-traffic car roads rather than being developed specifically for cycle paths. The empirical-based models to calculate the estimated traffic load compared to the permitted traffic load are not accurate for structures with thin asphalt pavements (<75mm). Models that better describe the behaviour of thin asphalt structures, especially with respect to climate, should be developed. It should also be further investigated if the maximum load criterion is optimal with respect to the heavy vehicles that exert this load. The risk of damage to the structure from such extreme loads is at its highest when the load bearing capacity of the structure is at its lowest, i.e., the spring thawing period. More studies need to be conducted to determine the load bearing capacity of cycle path structures with different runoff and drainage conditions in this period of the year. The condition assessment manual Bära eller brista should also be updated with a section on root infiltration of cycle paths.